The present invention relates to a new and improved method for determining displacements or shifts in the ground or terrain, in rocks, in structures and the like, wherein there is determined the relative position between neighboring measuring locations arranged at a mutual spacing at the medium which is to be examined. The invention further pertains to novel apparatus for the performance of the aforesaid method and is of the type comprising a number of measuring locations arranged in mutually spaced relationship from one another in the medium to be examined. The invention also is concerned with a measuring probe or sensor which is suitable for use in the apparatus of the invention.
With heretofore known equipment of the aforementioned type for measuring shifts in the ground, in rocks or in structures or buildings, for instance by means of a chain extensometer available from the firm Interfels Company, there are fixedly installed measuring heads at the measuring locations of the medium to be examined. Neighboring measuring heads are connected with one another such that there can be detected a lengthwise or spacing change from one measuring head to another measuring head. These stationary devices have, among other things, the drawback that there must be installed at each measuring location a number of measuring heads. These measuring heads cannot or only partially can be reclaimed. Therefore when there are involved a large number of measuring locations an appreciable expenditure in equipment is required. Additionally, these measuring heads, after having been installed, are only at best, if at all, accessible with difficulty, thereby rendering their maintenance and control problematic, if not in fact totally impossible.
Apart from the foregoing, there are also known to the art measuring devices for the determination of displacements or shifts wherein, by means of a probe, there is detected the position of metallic rings arranged at a mutual spacing from one another in a tube. This tube is installed in the medium to be examined. This system is known as the radio peak probe system IDEL of the aforementioned Interfels Company. Upon passage of the probe through one of the metallic rings there is generated a signal, enabling determination of the location of such metallic ring and its position with respect to a reference peak. With one and the same probe it is possible to undertake measurements at different measuring locations or sites, but the measurements can only be accomplished with relatively small accuracy, and therefore, only can be practically employed for making the requisite determinations when great shifts or displacements are involved.